1. Technical Field
The present invention relates to improving adhesion between thin films, and more particularly to methods and devices made thereby which employ a self-organizing diblock copolymer film employed as an etch mask to transfer holes into an underlying layer.
2. Description of the Related Art
Interface adhesion of thin films used in state of the art integrated circuit processing is often inadequate, especially when subjected to chemical-mechanical planarization (CMP). The existence of weak interfacial coupling in multilayer thin film stacks can lead to shear failure as a result of CMP, large temperature excursions, and the addition of tensile or compressive film layers to the stack. This problem can limit the yield and reliability of modern integrated circuits. In extreme cases, the lack of adhesion can produce catastrophic delamination, which not only damages the on-wafer circuitry, but may also contaminate/damage tooling. These problems are most acute when the poorly adhering materials possess relatively smooth interfaces.
Referring to FIGS. 1A and 1B, an example MRAM (Magnetic Random Access Memory) structure 10 is illustratively shown in its undamaged state (FIG. 1A). The MRAM structure 10 includes a substrate 12 with a metal plate 14 formed thereon. An MRAM device 16 is topped with an integrated hard mask 17. A dielectric adhesion layer 18 is formed thereon followed by an interlevel dielectric layer 20. FIG. 1B shows delamination of the interlevel dielectric layer 20 and/or the adhesion layer 18 due to stressful conditions during processing or operation.
In some cases, the identification and inclusion of a thin dielectric adhesion promoting layer as indicated in FIGS. 1A and 1B can reduce the delamination problem, but further improvement is still desirable.